Loops in C

Programming languages provide various control structures that allow for more complicated execution paths.

A loop statement allows us to execute a statement or group of statements multiple times.

Types of Loop

There are 3 types of Loop in C language:

1. while loop

2. for loop

3. do while loop

1. while loop 

while loop can be addressed as an entry control loop.

Syntax :

variable initialization;

while(condition)

{

    statements;

variable increment or decrement;

}

Example:

#include<stdio.h>

void main( )

{

    int x;

    x = 1;

    while(x <= 10)

    {

        printf("%d\t", x);

        x++;                          /* x = x+1, increment x by 1*/

}

}

2. for loop

for loop is used to execute a set of statements repeatedly until a particular condition is satisfied. We can say it is an open ended loop.

Syntax: 

for(initialization; condition; increment/decrement)

{

statement-block;

}

Example:

#include<stdio.h>

void main( )

{

    int x;

    for(x = 1; x <= 10; x++)

    {

        printf("%d\t", x);

}

}

3. Nested for loop

Syntax: 

for(initialization; condition; increment/decrement)

{

    for(initialization; condition; increment/decrement)

    {

        statement ;

}

}

Example:

#include<stdio.h>

void main( )

{

    int i, j;

    for(i = 1; i < 5; i++)            /* first for loop */

    {

        printf("\n");

        for(j = i; j > 0; j--)      /* second for loop inside the first */

        {

            printf("%d", j);

        }

}

}

4. do-while loop

In some situations it is necessary to execute body of the loop before testing the condition.

Syntax:

do

{

    .....

.....

}

while(condition);

Example:

#include<stdio.h>

void main()

{

    int a, b;

    a = 5;

    b = 1;

    do

    {

        printf("%d\t", a*b);

        b++;

    }

while(b<= 10);

}

Loop control statements : Loop control statements are used to change the normal sequence of execution of the loop

Statement	Syntax	Description
break statement	break;	Is used to terminate loop or switch statements.
continue statement	continue;	Is used to suspend the execution of current loop iteration and transfer control to the loop for the next iteration.
goto statement	goto  labelname; labelname : statement;	It transfers the current program execution sequence to some other part of the program.